The present disclosure relates to a quantum encryption communication apparatus, a quantum encryption communication method, and a quantum encryption communication system, and more particularly, to a miniaturized quantum encryption communication apparatus performing quantum encryption communication, which is capable of being mounted on a portable electronic apparatus or the like.
In the related art, in a communication performed in the Internet or the like, security has been kept by an encryption technique. The encryption systems are mainly divided into two encryption systems of a common key encryption system and a public key encryption system. For example, at present, AES (Advanced Encryption Standard) or the like has been widely used as the common key encryption system, and RSA or the like has been widely used as the public key encryption system.
In the common key encryption system, two parties that perform communication retain a common secret key. A transmitter encrypts a plaintext by using the secret key to generate a ciphertext, and a receiver decodes the ciphertext by using the same secret key to obtain the original plaintext.
In the common key encryption system, the important factor in the retaining of security is to keep the secret of the key. In the common key encryption system, if so-called “brute-force attack” which searches for the key by the brute-force is made, the key is revealed with a high probability. In the common key encryption system which is used at present, it is estimated that an impractically large amount of resources (performance of computation or an amount of computation) for making the brute-force attack would be necessary. Therefore, at present, it may be considered that the common key encryption system is safe. However, in the future, it may be predicted that the brute-force attack is a practical attack due to improvement in the performance of computers or the like. In fact, it is recommended that a method called 2-key TDES (Triple DES) which has been used in the related art be replaced by the AES.
With respect to an attack including the brute-force attack, the security is reinforced by using a method of frequently updating the common key. In other words, although an attacker eavesdrops on the communication and acquires a key, if the key is frequently updated, the amount of the ciphertext which may be deciphered with the key is reduced, so that the overall amount of the information which is acquired by the attacker is relatively lowered.
As one of the methods of frequently updating the common key, as disclosed in Japanese Patent No. 4015385, a method of performing quantum key distribution (QKD: Quantum Key Distribution) by using quantum encryption communication is proposed. The quantum key distribution is a protocol which generates a common secret key between the two parties which are connected by a communication line which may transmit quantum state and a general communication line. The protocol is based on quantum mechanical principles. Therefore, although an attacker eavesdrops on the communication line, it is considered that the information on the generated secret key is not leaked to the attacker. If the quantum key distribution protocol is used, the secret key may be safely shared by the two parties which are separated from each other, and the key may be generated at any time by using the quantum key distribution protocol, so that the aforementioned updating of the common key may be frequently performed. In this manner, by combining the quantum key distribution and the common key encryption, it is possible to reinforce the security of the common key encryption system.
In the quantum key distribution, for example, the BB84 protocol or the 6-state type protocol as an extension of the B84 protocol disclosed in “Secret key can be obtained from both compatible and incompatible measurements in the six-state QKD protocol” (Matsumoto Ryutaro, IEICE Technical Report IT2007-43, ISEC20070140, WBS2007-74 (2008-02)) has been used. In addition, as disclosed in Japanese Unexamined Patent Application Publication No 2007-286551, a decoy method is used where the intensity modulation of the light pulse is performed, so that it is possible to further increase the encrypted intensity of the quantum key distribution.